QIAGEN Paternity Testing Solutions

QIAGEN Paternity Testing Solutions 09/2016 9 cases Deficiency paternity cases The major advantage of ChrX markers arises in deficiency paternity cases (i.e., when a biological sample from a putative father is not available and DNA from paternal relatives has to be analyzed instead). When female individuals have the same father, they also share the same paternal ChrX. An investigation of ChrX markers of two sisters or half-sisters can thus exclude paternity, namely through the presence of four different alleles or haplotypes, even when none of the parents is available for testing. Autosomal markers cannot provide such information. Paternity cases involving blood relatives In paternity cases involving close blood relatives, such as alternative putative fathers, the exclusion power of STRs is sub- stantially decreased and ChrX STRs may be superior to autosomal markers. For example, if two alleged fathers are father and son, they would not share any X-chromosomal alleles identical by descent so that ChrX markers would be more efficient than autosomal markers. Paternity testing in rape and incest cases After incest or criminal sexual assault, medically indicated abortion may terminate the pregnancy. By using ChrY markers, efficient paternity testing of such material is possible for male fetuses. For female fetuses in contrast, only autosomal and ChrX markers can be analyzed, the latter of which represent a more efficient means of paternity exclusion. Positive proof of paternity, however, relies mainly upon fetal alleles not shared with the mother. Maternity testing In some circumstances, mother/child testing may be necessary. Although mitochondrial DNA sequencing can resolve maternity, this technology is not available in all laboratories, is still expensive, and sometimes does not provide the level of certainty required in paternity and forensic science. For testing mother-daughter relationships, ChrX markers are equivalent to autosomal markers and do not provide any specific advantage. Testing mother-son kinship, however, is more efficiently performed using ChrX markers. The exclusion chance in such cases is identical to that of ChrX STRs in father/daughter tests (Table 8). No. Formula and explanation Reference I MEC (mean exclusion chance) for AS markers in trios 1 II MEC for ChrX markers in trios involving daughters 2 III MEC for ChrX markers in trios involving daughters (Desmarais) 3 IV MEC for ChrX markers in father/daughter duos 3

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